(Kingston, ON) – Ninety per cent of the lakes surveyed in a new study
of Ontario’s “cottage country” north of Toronto have seen a significant
rise in taste and odour-causing algae – most dramatically in the past 20
years, the researchers report.

One of the most frequent complaints voiced by cottagers to local officials
is that water in their lakes periodically tastes or smells bad.

A common cause of such problems is blooms of small algae (microscopic
plants) that thrive in some of these lakes. Although the frequency of taste
and odour complaints seems to be growing steadily, it is unclear whether
the problems themselves are increasing or if local users are more sensitized
to these issues.

A study published in the current edition of the scientific journal Freshwater
Biology examines sediment from 50 lake bottoms in the Muskoka-Haliburton
region of Ontario. The results show taste and odour-causing algae have increased
in 90 per cent of these lakes since the early 1800s, with a marked rise over
the past two decades.

This phenomenon can’t be blamed solely on “local human impact,”
says team member John Smol, Canada Research Chair in Environmental Change
and co-head of Queen’s University’s Paleoecological Environmental Assessment
and Research Laboratory (PEARL). “It’s a complex of patterns, which we think
involves some combination of acidic deposition and climate change,” explains
Dr. Smol.

“The timing indicates that these patterns are the result of one or more
human-caused stresses operating at a broad, regional scale,” says lead investigator
Andrew Paterson, a former doctoral student at Queen’s. “We present new evidence
suggesting that disturbances such as acid rain and climatic warming may produce
significant, unprecedented changes to the algae of inland lakes, with important
implications for water quality.”

Lake water that smells and tastes foul can be traced to a variety of sources,
including chemical pollution and dead fish, but the most common cause is
a group of algae called chrysophytes. These microscopic organisms produce
scales and spines made of glass that are well preserved in lake sediment.
Through an analysis of sediment cores, the researchers were able to reconstruct
the history of these lakes, and compare the distribution of chrysophyte algae
over different time periods. Their study shows that substantial increase
began in the 1930s-1950s, with the sharpest rise over the past two decades.

“This is a classic example where environmental issues have been debated,
and decisions made, based on very short-term data sets – typically two to
three years,” says Dr. Smol. “Yet most of the answers lie much further back
in time. These sediment records are extremely valuable, because no one was
measuring algae 80 or 100 years ago.”

Also on the research team are biologists Brian Cumming from Queen’s and
Roland Hall from the University of Waterloo. Funding for the study was provided
by an Ontario Graduate Scholarship program, the Ontario Ministry of the Environment,
and the Natural Sciences and Engineering Research Council (NSERC).

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